We have identified an autosomal locus in the mouse which influences tissue levels of the lysosomal enzyme Beta-Galactosidase. Inbred strains of two genotypes have been identified; the specific activity of all tissues of strains carrying the Gsda allele (CH3/JHe) is twice that of strains carrying the Gsdb allele (DBA/J2). Preliminary studies have failed to demonstrate any structural differences between enzymes from these strains. We now propose to investigate the molecular mechanism of action of the Gsd locus. By immunochemical techniques with anti-Beta-Galactosidase serum, we will investigate the following points: 1) Does the Gsd locus alter the quantity of Beta-Galactosidase protein in mouse tissues? 2) Does the Gsd locus regulate the rate of synthesis or degradation of Beta-Galactosidase? 3) Is there a subtle difference in structure between enzyme encoded by these two alleles at the Gsd locus? Similar studies will also be carried out with a strain carrying a liver-specific developmental variant (C57BL/J6). The research proposed will contribute to the growing body of information on mechanisms of genetic regulation in mammalian.